Apparatus for actuating an electrical switching device

ABSTRACT

The invention relates to a device for actuating an electrical switchgear comprising at least one mobile contact point driven by a rotary shaft. According to the invention, an electric motor comprising a rotating drive shaft can be coupled to the rotary shaft by means of a transmission, in order to drive the same.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §371 to PCT ApplicationNo. PCT/EP2003/010199, filed as an International Application on Sep. 13,2003, designating the U.S., the entire contents of which is herebyincorporated by reference in its entirety.

BACKGROUND

The invention relates to an apparatus for actuating an electricalswitching device, in particular a high-voltage power breaker, inaccordance with the precharacterizing clause of claim 1.

The invention further relates to a switching device, in particular ahigh-voltage power breaker, having an actuating apparatus according tothe invention.

RELATED ART

Conventional power breakers have a switching chamber having a fixed anda moving contact piece. The moving contact piece is in this case fixedto one end of an insulating rod, whose other end is connected to one endof an actuating lever. The other end of the actuating lever is fixed toa rotating shaft such that the moving contact piece is moved towards thefixed contact piece, or away from said fixed contact piece, owing to arotation of the rotating shaft. The length of the actuating lever isdimensioned such that the power breaker is switched on or switched offowing to a rotation of the rotating shaft through a specific angle.

The rotating shaft is often set in rotation by means of a mechanical orhydromechanical stored-energy spring mechanism; the drive is coupled toone end of a connecting rod, which is connected to the rotating shaft ofthe power breaker via a further lever. A linear or approximately linearmovement of the drive through a specific stroke in this case bringsabout a rotation of the rotating shaft through the predetermined angleand thus brings about a switching operation.

A mechanical or hydromechanical stored-energy spring mechanism of thistype has an energy store, which is, for example, in the form of amechanical spring energy store in the form of helical springs, spiralsprings, torsion springs or plate springs. This spring energy store isstressed with the aid of a winding motor.

In order to carry out a switching operation, the spring energy store isrelieved by releasing a latch, or by actuating a control valve, as aresult of which the spring energy is transmitted onto the connecting rodvia a gear mechanism, or via a hydraulic transmission medium, and thusthe required stroke is exerted on the connecting rod.

Such stored-energy spring mechanisms have a comparatively complex designcomprising many individual moving parts and have a comparatively highspace requirement. Furthermore, such mechanically moving parts which aresubject to friction in principle require regular maintenance and checks.

BRIEF SUMMARY

The invention is based on the object of providing an apparatus foractuating a switching device, which has a simple design with a lowerspace requirement and requires little maintenance. It is also the objectof the invention to specify a corresponding switching device.

The object is achieved according to the invention by an actuatingapparatus having the features specified in claim 1. Further advantageousrefinements, and a corresponding switching device, are specified in thefurther claims.

According to the invention, an electric motor having a rotating driveshaft, which can be coupled to the rotating shaft of the switchingdevice by means of a gear mechanism, is provided for the purpose ofdriving a rotating shaft of an electrical switching device, inparticular a high-voltage power breaker. In comparison to a mechanicalor hydromechanical stored-energy spring mechanism, an electric motor hasa comparatively simple design and has a lower space requirement. Thecomplexity for its maintenance is also less than that for astored-energy spring mechanism. The use of a gear mechanism means thatthe torque which is transmitted onto the rotating shaft of the switchingdevice is greater than the torque which needs to be applied by theelectric motor. The physical shape and thus also the space requirementcan thus be further reduced compared to those of an electric motor whichdirectly drives the rotating shaft.

In the case of multi-pole, in particular three-pole, switching devices,a motor is provided for the purpose of driving all of the switch poles.

As an alternative, in the case of multi-pole, in particular three-pole,switching devices, a separate electric motor can also be provided forthe purpose of driving each switch pole.

The central axis of the drive shaft of the electric motor runs parallelto the central axis of the rotating shaft, for which reason the physicalarrangement of the electric motor is not fixed by the position of therotating shaft.

In one advantageous refinement of the invention, the electric motor isin the form of a servomotor. A servomotor has the advantage over otherelectric motors that, by corresponding driving, a comparatively preciserotation through a predetermined angle can be carried out. Furthermore,a servomotor, in particular during short-term operation, produces acomparatively high torque.

In accordance with one advantageous embodiment, the gear mechanism is inthe form of a lever mechanism. Such a lever mechanism, which is alsoreferred to as a four-membered rotary joint or as a rocker arm, isreliable and requires little maintenance.

The lever mechanism can advantageously be dimensioned such that arotation of the drive shaft of the electric motor through 180° bringsabout a switching operation. It is also possible to dimension the levermechanism such that a rotation of the drive shaft of the electric motorthrough less than 180°, for example 90°, brings about a switchingoperation. In such a case, however, the electric motor needs to apply acorrespondingly higher torque. With a rotation through 180°, the torqueto be applied by the electric motor is minimal.

In one advantageous development, an intermediate piece, which ispreferably in the form of a circular disk, is fixed on the drive shaftof the electric motor, it being possible for that end of the connectingrod which faces the drive shaft to be connected to the intermediatepiece at at least two distances from the central axis of the driveshaft. In this manner, the lever mechanism can be set to differentoutput angles by fixing the connecting rod at a suitable distance fromthe central axis of the drive shaft.

In accordance with one alternative embodiment, the gear mechanism can bein the form of a toothed belt drive, which is likewise comparativelyreliable and requires comparatively little maintenance.

The toothed belt drive advantageously has a transmission ratio of 1:1 to1:6, preferably 1:3.5. For a switching operation which requires, forexample, a rotation of the rotating shaft through 70°, the drive shaftof the electric motor will rotate through 70° to 420°, preferably 245°.A small rotation angle of the drive shaft requires a high torque of theelectric motor, and a large rotation angle requires a high angularvelocity. A mean value which is desired in practice is a rotation angleof approximately 245°, i.e. a gear transmission of 1:3.5.

Furthermore, a switching device, in particular a high-voltage powerbreaker, is claimed which has an actuating apparatus according to theinvention. The actuating apparatus can also be applied to furtherhigh-voltage, medium-voltage and low-voltage switching devices, forexample power breakers, disconnectors, grounding devices and loaddisconnectors.

The invention, advantageous refinements and improvements of theinvention and further advantages will be explained and described in moredetail with reference to the drawings, in which three exemplaryembodiments of the invention are illustrated and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an actuating apparatus according to the invention having alever mechanism with the switching device switched off,

FIG. 2 shows an actuating apparatus according to the invention having alever mechanism with the switching device switched on,

FIG. 3 shows a circular disk having a plurality of attachmentpossibilities, and

FIG. 4 shows an actuating apparatus according to the invention having atoothed belt drive.

FIG. 1 shows an actuating apparatus according to the invention having alever mechanism with the switching device switched off. A first lever 16is fixed to a drive shaft 18 of an electric motor, transversely withrespect to said drive shaft 18, and acts on a second lever 12 via aconnecting rod 14, said second lever 12 being fixed to a rotating shaft10 of a switching device, transversely with respect to said rotatingshaft 10. An actuating lever 42 is also fixed to the rotating shaft 10on the gas-chamber side, transversely with respect to said rotatingshaft 10, and actuates a moving contact piece of a switching chamber 40via an insulating rod 44. The switching chamber 40 is only illustratedsymbolically.

An imaginary connecting line V runs through the central axis of thedrive shaft 18 and the central axis of the rotating shaft 10. Animaginary center line M intersects the connecting line V and the centralaxis of the rotating shaft 10 at right angles.

In the illustration shown here, in which the switching device isswitched off, as can be seen from the symbol of the switching chamber40, the second lever 12 is inclined with respect to the center line Mthrough an acute angle α. In this case, that end of the second lever 12which is connected to the connecting rod 14 is located on that side ofthe center line M which faces away from the drive shaft 18. The firstlever 16 is aligned with the connecting line V, in which case its endconnected to the connecting rod 14 points in the direction of therotating shaft 10.

In order to switch the switching device on, the first lever 16 isrotated by the drive shaft 18 through an angle β, in this case 180°.During this rotation, the first lever 16, the connecting rod 14 and thesecond lever 12 are always located on the same side of the connectingline V.

FIG. 2 shows the actuating apparatus from FIG. 1 with the switchingdevice switched on, as can be seen from the symbol of the switchingchamber 40. The first lever 16 is again aligned with the connecting lineV, in which case, however, its end connected to the connecting rod 14points away from the rotating shaft 10. The second lever 12 is againinclined towards the center line M through the angle α, in which case,however, its end connected to the connecting rod 14 is located on thatside of the center line M which faces the drive shaft 18.

In order to switch the switching device off, the first lever 16 isrotated by the drive shaft 18 through the angle β, in this case 180°, inthe opposite direction to that during switching-on.

A rotation of the first lever 16 through 180° thus brings about arotation of the second lever through 2*α. The following is true for thedimensions of the lever mechanism:

L1=L2*sin(α), where L1 represents the length of the first lever 16, andL2 represents the length of the second lever 12. The length of theconnecting rod 14 is to be selected to be greater than the length of thesecond lever 12.

FIG. 3 shows an intermediate piece in the form of a circular disk 26having a plurality of attachment possibilities for a connecting rod 14.The circular disk 26 is mounted on the drive shaft 18 of the electricmotor, the central axes of the circular disk 26 and the drive shaft 18being aligned with one another. The circular disk 26 in this case hasfour holes 31, 32, 33 and 34, which are each fitted at a differentradial distance from the central axis of the circular disk 26 and act asattachment possibilities for the connecting rod 14. The connecting rod14 likewise has, for example, a hole such that the circular disk 26 andthe connecting rod 14 can be connected with the aid of a bolt.

The radial distance of the hole 31, 32, 33 or 34, with which theconnecting rod 14 is connected, from the central axis of the drive shaft18 corresponds to the length L1 of the first lever 16 in FIG. 1 and FIG.2. By the selection of the corresponding hole 31, 32, 33 or 34 forconnection to the connecting rod 14, it is thus possible to adapt thelever mechanism to different lengths L2 of the second lever 12 and/ordifferent rotation angles α of the rotating shaft 10. The circular diskis in this case to be aligned such that the hole 31, 32, 33 or 34, withwhich the connecting rod 14 is connected, lies on the connecting line Vand points towards the rotating shaft 10 when the switching device isswitched off.

The arrangement of the holes on the circular disk is freely selectable,as is illustrated by way of example by the arrangement of a first hole31 and a second hole 32. A third hole 33 and a fourth hole 34 arearranged, for example, such that their center points are aligned withthe central axis of the drive shaft 18.

The configuration of the intermediate piece is not restricted to theshape described here as a circular disk, rather the intermediate piecemay be in the form of, for example, a circle segment, an oval, a rod, atriangle, a rectangle or another shape.

FIG. 4 shows an actuating apparatus according to the invention having atoothed belt drive. A first belt pulley 24 is mounted on the drive shaft18 of the electric motor, and a second belt pulley 22 on the rotatingshaft 10 of the switching device. A toothed belt 20 is stretched aroundthe belt pulleys 22 and 24. An actuating lever 42 is also fixed to therotating shaft 10, transversely with respect to said rotating shaft 10,and actuates a moving contact piece of a switching chamber 40 via aninsulating rod 44. The switching chamber 40 is only illustratedsymbolically.

The transmission ratio of the toothed belt drive is given as a quotientof the radius of the first belt pulley 24 and the radius of the secondbelt pulley 22. If the transmission ratio is 1:3, a switching operationin which the rotating shaft 10 is to be rotated through, for example,70°, takes place owing to a rotation of the drive shaft 18 through 210°.

LIST OF REFERENCES

-   10: rotating shaft-   12: second lever-   14: connecting rod-   16: first lever-   18: drive shaft-   20: toothed belt-   22: second belt pulley-   24: first belt pulley-   26: circular disk-   31: first hole-   32: second hole-   33: third hole-   34: fourth hole-   40: switching chamber-   42: actuating lever-   44: insulating rod-   α: rotation angle of the rotating shaft-   β: rotation angle of the drive shaft-   M: center line-   V: connecting line

1. An actuating apparatus comprising: an electrical switching devicehigh-voltage power breaker having at least one moving contact piece, theat least one moving contact piece being driven via a rotating shaft thatrotates about a first axis; an electric motor having a rotating driveshaft that rotates about a second axis, which is coupled to the rotatingshaft of the switching device through a gear mechanism, wherein thedrive shaft of the electric motor drives the rotating shaft to switchthe switching device high-voltage power breaker on and off, wherein thefirst axis of the drive shaft runs parallel to the second axis of therotating shaft in a common horizontal plane, and wherein the gearmechanism is a lever mechanism connected to the rotating shaft and thedrive shaft.
 2. The apparatus as claimed in claim 1, wherein, in thecase of multi-pole, switching devices, an electric motor is provided forthe purpose of driving all of the switch poles.
 3. The apparatus asclaimed in claim 2, wherein the gear mechanism is in the form of atoothed belt drive.
 4. The apparatus as claimed in claim 3, wherein thetoothed belt drive has a transmission ratio of 1:1 to 1:6.
 5. Aswitching device having at least one apparatus for actuating purposes asclaimed in claim
 4. 6. The apparatus as claimed in claim 3, wherein thetoothed belt drive has a transmission ratio of 1:3.5.
 7. The apparatusas claimed in claim 1, wherein, in the case of multi-pole, switchingdevices, a separate electric motor is provided for the purpose ofdriving each switch pole.
 8. The apparatus as claimed in claim 1,wherein the first axis of the drive shaft runs parallel to the secondaxis of the rotating shaft.
 9. The apparatus as claimed in claim 1,wherein the electric motor is a servomotor.
 10. The apparatus as claimedin claim 1, wherein the lever mechanism is dimensioned such that arotation of the drive shaft of the electric motor through at most 180°brings about a switching operation of the switching device.
 11. Theapparatus as claimed in claim 1, wherein an intermediate piece,configured as a circular disk, is fixed to the drive shaft of theelectric motor, and wherein an end of a connecting rod which faces thedrive shaft is connected to said intermediate piece at one of at leasttwo distances from the first axis of the drive shaft.
 12. The apparatusas claimed in claim 1, wherein the gear mechanism is in the form of atoothed belt drive.
 13. The apparatus as claimed in claim 12, whereinthe toothed belt drive has a transmission ratio of 1:1 to 1:6.
 14. Theapparatus as claimed in claim 12, wherein the toothed belt drive has atransmission ratio of 1:3.5.
 15. A switching device having at least oneapparatus for actuating purposes as claimed in claim
 1. 16. Theapparatus as claimed in claim 1, wherein the electric motor is aservomotor.
 17. The apparatus as claimed in claim 16, wherein the gearmechanism is a lever mechanism.
 18. The apparatus as claimed in claim17, wherein the lever mechanism is dimensioned such that a rotation ofthe drive shaft of the electric motor through at most 180° brings abouta switching operation of the switching device.
 19. The apparatus asclaimed in claim 18, wherein an intermediate piece configured as acircular disk, is fixed to the drive shaft of the electric motor, andwherein an end of a connecting rod which faces the drive shaft isconnected to said intermediate piece at one of at least two distancesfrom the first axis of the drive shaft.
 20. A switching device having atleast one apparatus for actuating purposes as claimed in claim
 19. 21.The apparatus of claim 1, wherein the lever mechanism has one end fixedto the drive shaft of the electric motor and another end fixed to therotating shaft of the switching device.